loss of orgasms?

i have always been able to orgasm with my husband, i could probably count on one hand the amount of times i didn’t cum. and every time it’s achievable by penetration (i know, how lucky!) however the past few times we’ve had sex i haven’t been able to cum. i’ll usually feel the build up but then it goes away.

any ideas as to why this may be happening or how to fix it? 😭